Merged revisions 3049-3051,3053-3054,3058,3070,3074-3077,3082,3086-3088,3091-3092,3094-3095 from stable branch.

- Installer adds Apache and nginx user to ispapps group.
- Installer makes sure that /var/www/apps has 755 permissions.

- OpenSUSE: check if the line "include /etc/nginx/sites-enabled/*.vhost;" exists in /etc/nginx/nginx.conf before it is inserted (installation).

- replace double-quotes with single-quotes whenever appropriate
- fix indentation

- Added a fix for opensuse regarding issue: FS#1250 - smtp file in pam.d directory on some distributions is world readable.

- added installation instructions for opensuse 11.2 with bind and dovecot
- fixed a bug in bind plugin.
- improved opensuse installer.

Fixed a problem with broken tolower function in maildrop when compiled with some specific gcc settings by forcing lowercase addresses in master.cf and adding a workaround in case that tolower returns a empty result.